Hebrews 10:34

‘For you both had compassion on those who were in bonds, and took joyfully the spoiling of your possessions, knowing that you have for yourselves a better possession and an abiding one.'

Indeed they had visited those who had been imprisoned, taking them food and offering encouragement, (prisoners were dependent on food brought in by friends and family), in spite of the danger to themselves, and had joyfully looked on in a state of exaltation while their own possessions were despoiled, for they had known that they looked forward to a better possession and one that would last for ever that nothing could touch. This better possession was ‘eternal life', the life of Christ now presently enjoyed, which made them citizens of Heaven now, and would guarantee Heaven in the future.

Thus by their behaviour they had revealed something of what it meant to be a genuine Christian. This was why he could not believe that they would now desert Christ. For no genuine Christian who had been willing to face such things in triumph, could surely renege on Christ. These were things that accompanied God's saving work in the heart (see on Hebrews 6:9), and that nothing could take away. As John said, ‘we know that we have passed from death to life because we love our brothers and sisters in Christ' (1 John 3:14).